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1.
现在被广泛公认的由Fredlund提出的非饱和土力学的双参数理论,即净应力和吸力为非饱和土的应力状态量,不能直接考虑饱和度或含水率对非饱和土的应力-应变关系和强度的影响。在非饱和土三轴试验结果表明,即使在净应力和吸力路径相同的条件下,具有不同饱和度试样的应力-应变关系和强度也是不同的。其他条件相同时,试样饱和度越高,其应力比-应变关系曲线越高,强度越大。最新的水力-力学特性耦合的弹塑性本构模型可以定量地表示上述非饱和土的性质 相似文献
2.
非饱和土的水力和力学特性及其弹塑性描述 总被引：6，自引：3，他引：3
简单回顾了非饱和土本构模型研究的发展历程,总结了近几年非饱和土弹塑性本构模型最新研究成果,重点介绍了能统一模拟非饱和土水力性状和力学性状耦合的弹塑性本构模型。通过对建立模型过程中的几个核心问题讨论,较详细地说明该类模型的结构、性能以及相关问题。非饱和土水力性状的滞回性用假定存在饱和度弹性区间的弹塑性过程来模拟;该类耦合模型不仅考虑了吸力对非饱和土水力性状和力学性状的影响,还考虑了饱和度对应力-应变关系和强度的影响以及土体变形对土-水特征曲线的影响。用同一套模型参数,耦合模型可统一预测在吸力控制或含水率控制下沿各种应力路径下非饱和土的水力-力学特性,并简单介绍了膨胀性非饱和土的弹塑性本构模型以及耦合模型在有限元数值计算中的应用。 相似文献
3.
目前大多数非饱和土的弹塑性本构模型用非饱和击实土的试验结果进行验证,但现场其他类型的土,如沉积土经常有在非饱和状态下外部环境变化的情况。现有的非饱和土弹塑性模型是否适用于沉积土一类的现场土是需要研究的课题。进行非饱和上海第③层土的吸力控制排水排气三轴剪切试验,使用文中提出的能统一考虑非饱和土水力性状和力学性状的弹塑性本构模型,预测上述三轴试验结果,并与试验数据进行比较。比较结果显示,建立的本构模型能够很好地预测非饱和上海软土的水力和力学性质,说明该模型不仅可以适用击实土的预测,还能够很好地适用于其他类型非饱和土的水力和力学性质的模拟。 相似文献
4.
《岩土力学》2021,(2)
建立非饱和土在动态荷载作用下的本构模型有助于解决相关的工程问题。在塑性增量流动理论框架内,将BBM(BarcelonaBasicModel)模型与笔者提出的塑性硬化准则相结合,考虑控制吸力的循环荷载作用,建立了一个描述非饱和黏性土的弹塑性双面模型。该模型包含一个边界面和一个几何相似的加载面,二者结合记忆中心的概念,共同描述应力路径周期性改变加载方向时非饱和土的非线性、循环塑性和变形累积特性。采用动三轴剪切试验确定了一种非饱和粘质粉土的动态力学特性,分析了吸力、净围压和动应力幅值对循环塑性的影响。模型预测与非饱和土在静、动态加载下的试验结果的对比显示,二者吻合较好,表明所建弹塑性双面模型能够模拟非饱和土在控制吸力循环荷载作用下的力学行为。 相似文献
5.
《岩土力学》2020,(2)
建立非饱和土在动态荷载作用下的本构模型有助于解决相关的工程问题。在塑性增量流动理论框架内,将BBM(Barcelona basic model)模型与笔者提出的塑性硬化准则相结合,考虑控制吸力的循环荷载作用,建立了一个描述非饱和黏性土的弹塑性双面模型。该模型包含一个边界面和一个几何相似的加载面,二者结合记忆中心的概念,共同描述应力路径周期性改变加载方向时非饱和土的非线性、循环塑性和变形累积特性。采用动三轴剪切试验确定了一种非饱和黏质粉土的动态力学特性,分析了吸力、净围压和动应力幅值对循环塑性的影响。模型预测与非饱和土在静、动态加载下的试验结果的对比显示,二者吻合较好,表明所建立的弹塑性双面模型能够模拟非饱和土在控制吸力循环荷载作用下的力学行为。 相似文献
6.
吸力历史对非饱和土力学性质的影响 总被引：1，自引：0，他引：1
现在被广泛公认的由Fredlund提出的非饱和土力学的双参数理论,即净应力和吸力为非饱和土的应力状态变量,不能直接考虑吸力历史及其饱和度对非饱和土的应力-应变关系和强度的影响。非饱和土三轴试验结果表明,即使净应力和吸力相同的条件下,经过干-湿循环试样与未经过干-湿循环试样的应力比-应变关系和强度是不相同的。在其他条件相同时,经历过干-湿循环的试样比未经过干-湿循环试样的应力比-应变关系要高、强度大和体变小。经过干-湿循环试样的饱和度低而强度高,主要是由于经过先期较高的吸力,相当于受过较大的前期有效压力,使试样成为超固结土。更多不同吸力历史的对比试验有待于进一步研究,以便为非饱和土的水力-力学特性耦合弹塑性本构模型定量地表示上述非饱和土的性质提供基础性试验数据。 相似文献
7.
热-水-力耦合作用下非饱和土变形特性的弹塑性模拟 总被引：1，自引：0，他引：1
《岩土力学》2017,(4):1060-1068
在已有的非饱和土水-力耦合模型基础上,耦合考虑温度影响,建立了一个热-水-力耦合作用下非饱和土弹塑性本构模型。该模型以土骨架平均应力、修正吸力和温度为应力状态变量,以土骨架应变、饱和度和熵为应变状态变量。通过引入与温度相关的屈服面(LY、TY)以及相应的硬化规律来考虑温度对土体变形的影响。利用建立的模型,对文献中不同吸力和温度条件下的等向压缩和三轴排水剪切试验进行预测,预测结果表明,该模型能够较好地定量描述热-水-力耦合作用下非饱和土的变形特性。 相似文献
8.
将SFG模型中的加载湿陷屈服面（LC屈服面）与BBM模型中提出的吸力增加屈服面（SI屈服面）统一成为单独光滑的屈服面,基于弹塑性理论框架,推导出相应的弹塑性本构模型。通过非饱和固结直剪试验对江西红土的模型计算参数的应力-应变曲线与试验结果进行对比。结果表明：模型对多种应力路径下非饱和三轴试验的计算结果与相应试验的测定结果较为吻合,验证了模型能较好地模拟非饱和土在多种应力路径下的体应变行为。统一屈服面简化了加载湿陷屈服面与吸力增加屈服面之间的耦合分析,解决了因双屈服面的不连续而造成计算不便问题,拓宽了SFG模型的适用性。 相似文献
9.
10.
《岩土力学》2021,(2)
本文将SFG模型中的加载湿陷屈服面(LC屈服面)与BBM模型中提出的吸力增加屈服面(SI屈服面)统一成为单独光滑的屈服面,基于弹塑性理论框架,推导出相应的弹塑性本构模型。通过非饱和固结直剪试验对江西红土的模型计算参数进行测定。将计算参数输入模型程序并通过程序对已发表文献中非饱和三轴试验的应力路径进行计算,并将模型计算得到的应力-应变曲线与试验结果对比后得出结论:模型对多种应力路径下非饱和三轴试验的计算结果与相应试验的测定结果较为吻合,验证了模型能较好的模拟非饱和土在多种应力路径下的体应变行为。统一屈服面简化了加载湿陷屈服面与吸力增加屈服面之间的耦合分析,解决了因双屈服面的不连续而造成计算不便问题,拓宽了SFG模型的适用性。 相似文献
11.
杭州湾浅层储气砂土应力路径试验研究 总被引：2，自引：0，他引：2
利用GDS非饱和三轴试验系统开展了杭州湾储气砂土主动压缩、被动压缩、主动伸长与被动伸长等4种应力路径试验研究,以论证应力路径对非饱和砂土的变形性状与强度特性影响。结果表明,在卸荷应力路径被动压缩与被动伸长下非饱和砂土的应力-应变曲线呈明显的应变软化性状,而加荷应力路径主动压缩与主动伸长则分别表现为轻度应变软化及显著应变硬化变形特征;非饱和砂土的强度参数在卸荷与加荷应力路径中也存在差异,前者的有效凝聚力高于后者,而内摩擦角则相反;但其表观凝聚力与基质吸力关系在不同应力路径下均可用乘幂函数 有效描述,而试验参数a、b值不同,公式 可合理地用于表述非饱和砂土的强度特性。 相似文献
12.
This paper presents a three‐dimensional elastoplastic constitutive model for predicting the hydraulic and mechanical behaviour of unsaturated soils. It is based on experimental results obtained from a series of controlled‐suction triaxial tests on unsaturated compacted clay with different initial densities. Hydraulic hysteresis in the water‐retention behaviour is modelled as an elastoplastic process, with the elastic part modelled by a series of scanning curves and the elastoplastic part modelled by the main drying and wetting curves. The effect of void ratio on the water‐retention behaviour is studied using data obtained from controlled‐suction wetting–drying cyclic tests on unsaturated compacted clay with different initial densities. The effect of the degree of saturation on the stress–strain‐strength behaviour and the effect of void ratio on the water‐retention behaviour are considered in the model, as is the effect of suction on the hydraulic and mechanical behaviour. The initial density dependency of the compacted soil behaviour is modelled by experimental relationships between the initial density and the corresponding yield stress and, thereby, between the initial density and the normal compression line. The model is generalized to three‐dimensional stress states by assuming that the shapes of the failure and yield surfaces in the deviatoric stress plane are given by the Matsuoka–Nakai criterion. Model predictions of the stress–strain and water‐retention behaviour are compared with those obtained from triaxial tests with different initial densities under isotropic compression, triaxial compression and triaxial extension, with or without variation in suction. The comparisons indicate that the model accurately predicts the hydraulic and mechanical behaviour of unsaturated compacted soils with different initial densities using the same material constant. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
13.
为了研究复杂应力条件下非饱和原状黄土的非线性本构模型,通过考虑真三轴条件下中主应力和吸力对大主应变的影响,提出了一个考虑中主应力影响的非饱和原状黄土的非线性本构模型。该模型包含12个参数,均可由常含水率非饱和土真三轴试验确定。研究了中主应力对土体变形和强度的影响,探讨了模型参数的变化规律。初始吸力一定时,土体的黏聚力随着中主应力的增大而增大,而内摩擦角随着中主应力的增大呈线性减小趋势。当吸力小于162 kPa时,吸力摩擦角等于21.8°;当吸力大于162 kPa时,吸力摩擦角等于5.5°。初始吸力相同时,不同中主应力条件下土体的体积模量可取为常数。利用该模型预估了常含水率真三轴等向固结试验的吸力变化规律,理论结果与试验结果比较接近。但是对于真三轴剪切试验吸力的预估还需要进行深入探讨。 相似文献
14.
Xiong Yong-lin Ye Guan-lin Xie Yi Ye Bin Zhang Sheng Zhang Feng 《Acta Geotechnica》2019,14(2):313-328
This study presents a sophisticated elastoplastic constitutive model for unsaturated soil using Bishop-type skeleton stress and degree of saturation as state variables in the framework of critical state soil mechanism. The model is proposed in order to describe the coupled hydromechanical behavior of unsaturated soil irrespective of what kind of the loadings or the drainage conditions may be. At the same time, a water retention characteristic curve considering the influence of deformation on degree of saturation is also proposed. In the model, the superloading and subloading concepts are introduced to consider the influences of overconsolidation and structure on deformation and strength of soils. The proposed model only employs nine parameters, among which five parameters are the same as those used in Cam-Clay model. The other four parameters have the clear physical meanings and can be easily determined by conventional soil tests. The capability and accuracy of the proposed model have been validated carefully through a series of laboratory tests such as isotropic loading tests and triaxial monotonic and cyclic compression tests under different mechanical and hydraulic conditions.
相似文献15.
在修正剑桥模型的基础上,提出了一个非饱和土毛细滞回与骨架变形耦合的弹塑性本构模型。该模型考虑了基质吸力与饱和度对屈服应力的影响,可以同时描述非饱和土的弹塑性变形特性与毛细循环滞回效应。根据塑性体变的产生使非饱和土进气值增大的特点,建立了变形对土-水特征曲线影响的数学描述。该模型有效地考虑了饱和度对前期屈服应力的作用,准确地反映了土体在不同土-水状态条件下（脱湿和吸湿过程）强度特性的变化,而且还可以有效地描述水力循环历史对土体变形的影响。通过与试验数据对比,证明了该模型能够模拟非饱和土的主要力学特性。 相似文献
16.
In the last decades, a number of hydro-mechanical elastoplastic constitutive models for unsaturated soils have been proposed. Those models couple the hydraulic and mechanical behaviour of unsaturated soils, and take into account the effects of the degree of saturation on the stress–strain behaviour and the effects of deformation on the soil–water characteristic response with a simple reversible part for the hysteresis. In addition, the influence of the suction on the stress–strain behaviour is considered. However, until now, few models predict the stress–strain and soil–water characteristic responses of unsaturated soils in a fully three-dimensional Finite Element code. This paper presents the predictions of an unsaturated soil model in a Three-dimensional Framework, and develops a study on the effect of partial saturation on the stability of shallow foundation resting on unsaturated silty soil. Qualitative predictions of the constitutive model show that incorporating a special formulation for the effective stress into an elastoplastic coupled hydro-mechanical model opens a full range of possibilities in modelling unsaturated soil behaviour. 相似文献
17.
This paper presents an elasto‐plastic model for unsaturated compacted soils and experimental results obtained from a series of suction‐controlled triaxial tests on unsaturated compacted clay with different initial densities. The initial density dependency of the compacted soil behaviour is modelled by establishing experimental relationships between the initial density and the corresponding yield stress and thereby between the initial density and the location and slope of normal compression line. The model is generalized to three‐dimensional stress states by assuming that the shapes of the failure surface and the yield surface in the deviatoric plane are given by the extended SMP criterion. A considerable number of the isotropic compression, triaxial compression and extension tests on unsaturated compacted clay with different initial densities were performed using a suction‐controllable triaxial apparatus, to measure the stress–strain–volume change in different stress paths and wetting paths. The model has well‐predicting capabilities to reproduce the mechanical behaviour of specimens compacted under different conditions not only in isotropic compression but also in triaxial compression and triaxial extension. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献